DFMBA试剂和XtalFluor试剂
2020-01-17 08:38:08   来源:

DFMBA试剂

N,N-二乙基-α,α-二氟-3-甲基苄胺有两个容易消除的氟原子, Hara报道了用DFMBA在糖类和核苷类氟化羟基的高收率的得到相应的氟代化合物。

p-t-Butylbenzaldehyde (162 mg, 1 mmol), DFMBA (426mg, 2 mmol), and Et3N-3HF (161 mg, 1 mmol) were introduced into a reactor of a TeflonTM PFA tube with a diameter of 10 mm sealed atone end. The open end of the reactor was connected to a reflux condenser. Then, the reaction mixture was submitted for 20 min to microwave irradiation and during the irradiation, the temperature was kept at 180 oC. After cooling, the reaction mixture was poured into an aqueous NaHCOsolution. The product was extracted with ether three times and the combined ethereal layers were dried over MgSO4. Purification by column chromatography (silica gel/hexane-ether) gave p-difluoromethyl-t-butylbenzene in 80% yield.

(Shingo Kobayashi, et al, Tetrahedron, 200460, 6923–6930)

XtalFluor试剂

XtalFluor-E 和XtalFluor-M是由 Couturier和他的同事在2010年报道了它们的制备和应用,它们是固体的氟化试剂,比DAST,Deoxo-Fluor有着更好的稳定性。不像DAST,Deoxo-Fluor和FLUOLEAD在反应中会释放出游离的氢氟酸,XtalFluor不会释放出游离的氢氟酸,因此可以在普通的玻璃瓶中做反应,它比DAST有着更好的选择性,同时能够显著减少消除的副产物。

To a solution of triethylamine trihydrofluoride (326 μL, 2.0 mmol) in dichloromethane(3.0 mL) at room temperature were successively added XtalFluor-E (344 mg, 1.5mmol) and 3-phenylpropionaldehyde (132 μL, 1.0 mmol). After 2 h, the reaction mixture was quenched at room temperature with a 5% aqueous sodium bicarbonate solution and stirred for 15 min, and the resulting mixture was extracted twice using dichloromethane. The organic phases were combined, dried over magnesium sulfate, and filtered through a pad of silica gel. Solvents were evaporated, and the resulting crude material was purified by silica gel flash chromatography using pentane to provide the title compound (119 mg, 76%) as a clear oil

示例:

To a solution of triethylamine trihydrofluoride (163 μL, 1.0 mmol) in 1,2-dichloroethane(2.0 mL) was added at room temperature XtalFluor-M (362 mg, 1.5 mmol) followed by 4-carbethoxycyclohexanone (159 μL, 1.0 mmol), and the reaction mixture was heated to reflux. After 2 h, the reaction mixture was cooled to room temperature, quenched with a 5% aqueous sodium bicarbonate solution, and stirred for 15 min,and the resulting mixture was extracted twice using dichloromethane. The organic phases were combined, dried over magnesium sulfate, and filtered through a pad of silica gel. Solvents were evaporated, and the resulting crude material was purified by silica gel flash chromatography using pentane to provide the title compound (166 mg, 86%) admixed with 4-carbethoxy-1-fluorocyclohex-1-ene(15:1 ratio respectively) as a clear oil

(L’Heureux,A. etal. J. Org. Chem201075,3401)

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